1. Field of the Invention
The present invention relates to an LED array head to be used for an apparatus such as an LED printer using an electro-photography process.
2. Description of the Prior Art
The prior art LED array head will be described with reference to FIG. 6.
In FIG. 6, the device includes a ceramic substrate 1 on which an LED chip 2 is disposed by the die bonding and a wire bonds 3 are disposed in the LED chip 2 for each light emitting section 2a so as to supply electric power thereto. In order to protect the LED chip against an interference from the external environment, a cover glass 33 is fixed onto the ceramic substrate 1. Above the light emitting section 2a of the LED chip 2, there is arranged a rod lens array 4 of the self-convergence type retained by a mechanism not shown, thereby collecting the light radiated from the light emitting section 2a onto such an object 5 to be exposed to the light as a photosensitive drum.
However, in the LED array head of the prior art, since the rod lens array of the self-convergence type 4 is utilized, the distance between the light emitting section 2a and the object 5 to be exposed to the light is determined by the focal length of the rod lens array of the self-convergence type 4 and is hence quite long.
In addition, only a portion of the light radiated from the light emitting section 2a reaches the rod lens array of the self-convergence type 4 and the efficiency of light transmission to the object 5 is not satisfactory; as a consequence, in order to increase the quantity of light, a great energy is required to radiate light to be supplied to the LED chip 2.